Sooo...I screwed up, I thought I drained the cooling system of straight water after the last time I ran my engine about a year ago...apparently I dident... I took off the upper radiator hose and I thought I opened the petcock but I dident, so only the upper radiator hose was disconnected. Yesterday I removed the lower radiator hose to change out the radiator (other issues)and the nastiest rusty water flowed out, I ran a water hose through the thromost housing but I'm sure there's more nastiness inside the block. what's the best way of getting it out the engine currently doesn't run and I don't want to contaminate the new rad..btw it has about 500 miles on the rebuild, and the reason it's not 50/50 and the reason I'm changing it out is the upper hose attachment cracked and it spewed everywhere and I limped it home on straight water

 

They used to make a "heavy duty cooling system flush" that was oxalic acid, and came with an additional container of "neutralizer". If y ou can find that, it's probably your best bet. Problem will be, how to legally get rid of 5 gallons of iron oxalate solution afterwards.

In any case you CANNOT POSSIBLY drain the block unless you remove the drain plugs. There is one on each side. The pass side one is cleverly disguised as the knock sensor (back in 1954 when the GM guys were looking ahead to the introduction of fuel injection, they disguised the knock sensor port as a coolant drain, to keep those lusers at Frod and Xler in the dark about what they were doing), excetly halfway from front to rear of the block (between #4 & #6 cylinders) about an inch above the oil pan rail. The driver's side one is directly opposite, between #3 & #5. They have a 9/16" head (from the factory anyway) and are ¼" pipe. They can be a real PITA to get out, as they are steel, and rust rather thoroughly to the cast iron of the block. Best to grab a new knock sensor while you're at it, and go the hardware store and pick up ac brass one, to replace them. Use pipe thread sealer, NOT teflon tape, on the knock sensor, and don't overtighten it. No more than about 12 - 15 ft-lbs on it. You can use the same sealer on the other one and tighten it a bit more like maybe 20 ft-lbs.

 

I figured I'd have to pull the water jacket plugs, thers no knock sensor so I less thing to worry about there, the million dollar queston is how do I do all this without hooking up the radiator ( the upper outlet weld completely failed on the old one wile taking it out so reusing that's a no go and I don't want to contaminate the new one) or running the engine

 

Best you can do in that case, is a flush. Take out the thermostat and block plugs; remove the rad & heater hoses, and plug up the holes in the engine; and blast it out with the highest possible pressure water, from the t-stat housing. Won't get everything out but it'll at least make a dent.

 

My truck had THE nastiest brown rust in the cooling system.

Honestly, you'll never get it out all at once... itll take many flushes, drive cycles etc... Just start with the above.
Then later down the line flush it out again... you can try that prestone radiator flush stuff... it works ok. But i had to do it several times.

You'll think its clean but later on all that grime will return again. Flush it again. Seems counterproductive but I ran straight water but used the truck a lot to heat up the crap a lot and flushed it all out.. like a few times a week (didnt let it sit) Cant imagine paying for coolant each time....


Then later on, if you have a water pump with one of those ports in it, remove that port plug and install a hose barb, and attach some hose to that and connect one of those garden hose flush kits onto it. Then you can flush it pretty thoroughly. I was flushing my 4.3 for a long time as brown crap constantly poured from the heater hose line (no heater core) direct from the motor. I ran the engine too to help it pump the gunk put / warm it up a bit.


Eventually it was as clean as can be,. i threw on a coolant filter as well and added a 50/50 of coolant and distilled water... years later my coolan is still beautiful!

 

You went through the winter with only water in the block?
Before you do any flushing, inspect the lower sides of both cylinder banks on the blocks for cracks.
This happened to a friend of mine. We were working on his Camaro on a warm t-shirt weather day.
We had only tap water in the block. That night it went down well below freezing.
He found ice in the upper radiator hose and radiator. He started the engine to warm it up and
water spewed out of the lower block on both sides. Cracked block = all done.

 

I saw that and cringed a bit too, If he lived near us in the northeast it'd have been done for before December, but he lives in Las Vegas, maybe he got lucky and it didn't get to freezing temps over the winter?

 

Look at post #47 and #48 for some context and follow-up technical tip. https://www.thirdgen.org/forums/cool...es-my-new.html

You can also review all the other posts above this for some ideas. It's a labor of love. I can't tell you had many times I had to flush to get t post #47. More than I can recall. Its a total mess for a while. I came out under the car soaking wet so many times! Bottom line, coolant is a protector, needs changed at prescribed intervals. Mine was in storage for a few decades, and that is how it got to this I would image.

 

sorry been busy the last couple days, its been in the garage most of the winter, and I need to update my profile apparently, I'm now stationed in Tucson AZ, so cracks shouldn't be a concern, so...based on what I've read...here's what I'm thinking of doing, pulling the water pump and blocking it off, breaking loose the block plugs to get the last bit of nastiness out and to verify they can come out and aren't siezed, mixing up a batch of coolant flush and poring it in through the thermostat housing and letting it sit as per the instructions, and draining it trough the block plugs, then flushing it with fresh water until it is 100* clean, and finally putting everything back together with green antifreeze....how does my plan sound to everyone, while the coolent flush is doing its thing I'm going to pull the packing off the water pump and see if the impeller took any rust damage (its an edelbrock endurashine high-flow one I would like to save it if I can) BTW...I'm replying through my phone, so if the typing is awkward thats why.

 

Maybe unblock the water pump ports too.